This study aims to investigate the use of de-novo designed Interleukin-like peptide for its efficacy in cancer treatment. The synthetic peptide was designed using the Resonant Recognition Model (RRM), which postulates that certain features within protein structures are critical for specificity of protein activity. It was shown that interleukin (IL) can significantly affect tumor progression. We designed and synthesized a bioactive peptide that can mimic the therapeutic activity of IL-12 protein. The activity of the de-novo designed peptide was tested on an adherent mouse skin cancer cell line (B16F0). Visible effects of this peptide on cancer cells, including morphological changes and apoptosis, were evaluated using phase contrast and fluorescent microscopy. The results revealed that the IL-12 peptide analogue was toxic to cancer cells as it affected their growth and survival causing apoptosis followed by detachment of the confluent cellular layer.